The present invention relates to a machine for inspecting glass or plastic containers such as bottles and more particularly to such a machine which can inspect the sidewall of the container to find defects.
The sidewall of a glass container can include various types of defects, including an area of unevenness in glass distribution which will provide a lensing effect when backlit (a refractive defect). Container inspection machines, such as shown in U.S. Pat. No. 5,004,909, inspect the sidewall of a glass bottle by presenting the bottle in front of a light source defined by alternating black and white stripes. Such an inspection machine can find refractive best when they are located at the edge of the stripe. Container inspection machines, such as shown in U.S. Pat. No. 4,601,395, inspect the sidewall of a glass container by presenting the bottle in front of a light source defined by a single bright area that is always in the view of the camera, with transversely spaced outer regions of various intensities and rotating the container.
It is an object of the present invention to provide a container-inspecting machine which will have a higher probability of detecting refractive defects without requiring the container to be rotated.
Other objects and advantages of the present invention will become apparent from the following portion of this specification and from the accompanying drawings which illustrate in accordance with the mandate of the patent statutes a presently preferred embodiment incorporating the principles of the invention.
The backlight for the inspection is created by using a spatially cyclically continuously varying intensity between the extremes of dark and light intensity. The rate of change is less than that required to be detected as a defect. Refractive defects in the container, through a lens effect, will present to the camera other parts of the light source in a compressed manner. This compression view of the source has a greatly increased rate of change of intensity and thus detected as a defect. The cyclic intensity nature of the illumination permits defect detection throughout the container.